SEA-CUCUMBERS. 
3*3 
the animal has become flattened, and the tube-feet restricted to three out of the 
five ambulacra, and by these three the animal creeps about, or holds itself fixed to 
the rock. A similar modification is carried to excess in the deep-sea holothurians 
known as Elasipoda. Here, as in the illustrated Scotoplarta, there are a couple of 
rows of thick tube-feet, forming little stumps, with which the animal moves, as a 
centipede moves by its legs. In front there is a sort of funnel or scoop formed by 
the short tentacles, while a few of the tube-feet form long horns or feelers on the 
upper side. In the deep-sea Psychropotes, on the other hand, mouth, vent, and 
tube-feet are confined to a flat sole; while the posterior part of the body is 
a deep-sea holothurian, Scotoplana (nat. size). 
extended in a long tail. Some holothurians live in mud; and by reason of 
constantly keeping both mouth and vent above the surface their bodies have 
become curved in U-fashion, as seen in the U-shaped Ypsilothuria (illustrated on 
p. 312). This is carried still further in the club-like Rhopalodina (illustrated 
on p. 314), a form shaped like a cherry, with a thick stalk; the openings of both 
mouth and vent being at the top of this stalk. A yet stranger modification is the 
holothurian described under the name Pelagothuria, which lives in the East 
Pacific, on the surface of the ocean. It has no calcareous spicules, the longitudinal 
muscles being mostly changed into a jelly tissue. Around the mouth the body is 
extended into a kind of disc, prolonged into thirteen to sixteen feelers. The 
animal swims by the movements of this disc. 
Holothurians have no means of offence, but protect themselves for the most 
part by assuming the colour of their surroundings. The huge Synapta besseli, 
which reaches a length of 6 feet, has a habit, when taken in the hand, of squeezing 
the fluid contents of its body towards the portion that is grasped, till it becomes 
too big to hold. Some, when much irritated, seem to fade away and dissolve by 
